Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 17: Poster: Crystallisation, Nucleation and Self assembly
CPP 17.11: Poster
Dienstag, 27. März 2012, 18:15–20:15, Poster A
Protein crystallization in the presence of di- and trivalent metal ions — •Andrea Sauter1, Georg Zocher2, Fajun Zhang1, Thilo Stehle2,3, and Frank Schreiber1 — 1Institut für Angewandte Physik, Universität Tübingen, Germany — 2Interfaculty Institute of Biochemistry, Universität Tübingen, Germany — 3Department of Pediatrics, Vanderbilt University, Nashville, USA
Structure determination of proteins requires high-quality single crystals. Our previous studies concerning reentrant condensation (RC) of proteins upon adding trivalent salts have opened up a way to a universal phenomenon that can be used to tune protein interactions and thus optimize protein crystallization [1,2]. RC is caused by ion binding at the protein surface and thus an effective charge inversion. We now investigated how globular proteins behave upon using divalent metal salts. A phase behaviour similar to RC is found for bovine β-lactoglobulin (BLG) with CdCl2 or ZnCl2. Zeta potential measurements show a charge inversion of the protein. However, no such behaviour could be observed for other proteins by adding divalent salts, indicating the specificity of BLG. We present the growth of BLG crystals using trivalent [3] or divalent ions and their structure determined by X-ray diffraction. The positions of the metal cations that bridge acidic side chains from neighbouring protein subunits were compared for different salts. Using BLG as a model system, the role of the di- and trivalent metal ions in protein crystallization is discussed. [1] F. Zhang et al., PRL, 101, 2008, 148101; [2] F. Zhang et al., Proteins, 78, 2010, 3450-3457; [3] F. Zhang et al., J. Appl. Cryst., 44, 2011, 755-762.